Process of producing hexamethylenetetramine



Patented June 24, 1924.4

UNITED STATES PATENT OFFICE.

CABNIE B. CARTER AND ALBERT E. COXE, F PITTSBURGH, PENNSYLVANIA, AB BIGNORS 10 B. KARPEN b BROS., 0F CHICAGO, ILLINOIS, A CORPOBATIQN 0F WEST VIRGINIA.

PROCESS 0F PBODUCING HEXAHETHYLENETETRAMINE.

No Drawing.

To all 'whom t mag/concern:

Be it known that we, CARNIE B. CARTER and ALBERT E. Coxn, citizens of the United States, residing at Pittsburgh, Allegheny 5 County, Pennsylvania, have invented a new and useful Im rovement in Processes of Producing examethylenetetramine, of which the following 1s a specification.

The present invention relates to the roduction of hexamethylenetetramine; an the primary object is to provide a s imple and practicable method of producing hexamethylenetetramine by condensing methy- 16 lene chloride with ammonia.

Methylene chloride is obtained as one of the chlorinated products when natural gas,

for example, is subjected to a chlorination process for the purpose of roducing I nethyl 20 chloride to be used in t e production of esters, as described in our pending appllcation No. 423,870, {iled November 13, 1920.

Thepresent method provides a use for `such methylene chloride as is formed in the 26 chlorination of the natural gas. According to this method, hexamethylenetetramine, which is widely used in the arts, may be easily and conveniently produced in very pure form.

30 Methylene chloride enters into reaction with liquid ammonia to produce ammonium chloride and hexamethylenetetramine, at temperatures as low as 20 to 25 C. The reaction may be represented by the following equation:

`im shan distinta-.a 61d bath While bein ifilled with li uid ammonia an partiall A that it all bediermetica y sealed before re- Appliotion led August 2B, 1922, Serial R0. 583,915.

moval from this bath. A bath of ycarbon dioxide snow and alcohol is suitable for the pur ose.

e tube thus prepared at first shows a. perfectly homogeneous liquid; the methylene chloride and liquid ammonia are miscible in all proportions. After standingy for a few hours (8-12) at room temperatures, however, the liquid beg-ins to separate into two layers, the smaller ayer forming at the to As time goes on the upper layer graduali;r grows larger and after ten daysv or two weeks the two layers have become about equal in volume. At this v oint c stals begin to s arate from the liquids, the liquids begin at t e same time to disappear, and as crystallization proceeds the two liquids radually disappear until the liquids are nally supplanted by a crystalline mass. Such an experiment extendsV over a period of several weeks.

The mass of crystals on examination `will be found to be a mixture of ammonium chloride and hexamethylenetetramine in the pro# portions of one mol. of hexamethylenetetramine to twelve mols. of ammonium chloride. The separation of the two constituents may be effected as follows: The entire mass is carefully and thoroughly extracted with chloroform in order to dissolve all hexamet lenetetramine; the ammonium chloride 1s not dissolved. Quantitative analyses of the chloroform solution and the residual crystalline mass will show that hexamethylenetetramine and ammonium chloride are present in the proportion of 1 mol. of hexamethylenetetramine to twelve mols. of ammonium chloride.

The time re uired for a com lete reaction between methylene chloride an ammonia at room temperature makes the reaction at such temperature impracticable from a manu facturing point of view. A temperature of 75 C. is quite satisfactory, although a somevwhath her temperature may bei used if desired. t a temperature of 100 C., the conversion is rough y proportionate to the time of theheating operation. For example, a mixture of the materials heated at a temperature of 100 C. for 5 hours shows a conversion of about 35.6 per cent; heated for ammonium chloride.

per cent; and heated for twenty hours, shows a conversion of substantially 100 per cent. The reaction may be carried out practically in somewhat less than 20 hours at 100 C. The time may be very much shortened by carrying out the reaction at a tem erature ,of 120 C. to 125 C. The critica temperature of ammonia is 130 C. and a temperature somewhat lower than this figure probably is desirable.

In practice, the manufacture of hexamethylenetetramine b this method may be carried out in the fo lowing way:

A given quantity of methylene chloride is placed in a strong metal autoclave; li uid ammonia is then pumped into the auto ave until suiiicient ammonia has been introduced to combine with all of the methylene chiloride to form hexamethylenetetramine and The theoretical proportions are 6 mols. of methylene chloride to 16 mols. of ammonia. In practice, an excess of ammonia may be used, say 100'per cent excess. The autoclave is heated at, 100 C. or higher for a eriod of 20 hours or less, depending on t e tem erature employed. Excess ammonia is distilled o' and recovered. The residual crystal mass is subjected to extraction with chloroform, carbon tetrachloride, or other suitable solvent, in any suitable extractor, to separate the hexameth# ylenetetrainine from the ammonium chlo ride. The hexamethylenetetramine thus obtained is of high purity, if pure ammonia and pure methylene chloride have been em plo ed, and requires no purification.

'Iyhe ammonium chloride is treated with hydrated lime and subjected to distillation in order to recover the ammonia.y The re-l covered ammonia is subsequently used in the formation of more hexamethylenetetramine.

From the description given it will be seen that only four of the 16 parts of ammonia used in the autoclave are actually consumed to form hexamethylenetetramine. The remaining 12 parts of ammonia react to forni ammonium chloride and this amonia is recoverable by the method stated.

The methylene chloride is employed as a liquid in the recess; and, as stated, liquid ammonia pre erably is employed.

In practice, the materials are ex elled from the autoclave and the excess o ammonia, where used, is withdrawn from the storage tank and compressed to form liquid ammonia and returned tol the liquid ammonia tank to be reused. Also, the ammonia recovered by treating ammonium chloride with hydrated lime in a still is re turned to the liquid ammonia storage tank to be reused.

As indicated, the hexamethylenetetramine is extracted from the mixture of hexamethlenetetramine and ammonium chloride by passing chloroform through the extracting chamber. The chloroform carrying the dissolved hexamethylenetetramine passes to a still by means of which the chloroform is driven oli' and the hexamethylenetetramine is recovered. The chloroform in the still passes back to the chloroform storage tank and from there passes again to the extractor, and thus is used over and over in the process.

The foregoing detailed description has been given for clearness of understandin only and no unnecessary limitations shoul be understood therefrom, but the appended claims should be construed as broadly as permissible in view of the prior art.

What we regard as new and desire to secure by Letters Patent is- 1. The process of producing hexamethylenetetramine which comprises: reacting upon methylene chloride with ammonia at. elevated temperature, in the absence of alco` hol, to form hexamethylenetetramlne and ammonium chloride and extracting the hexameth lenetetramine from the ammonium chlori e.

2. The process of producing hexamethylenetetramine which comprises: causing a reaction at elevated temperature between methylene chloride and ammonia in the presence of an excess of ammonia, which excess amounts to more than 50% of the theoretiC-al proportion, recovering the excess of ammonia, and extracting the hexamethylenetetramine formed from the ammonium chloride formed.

3. The process of producing hexamethylenetetramine which comprises:v causing a reaction at elevated temperature between methylene chloride and ammonia in the presence of anexccss of ammonia, such ex- 105 cess amounting tc'pmore than 50% of the theoretical proportion, recovering the excess of ammonia, extracting the hexainethylene- 4tetramine formed from the ammonium chloride formed, recovering the excess ammonia and the ammonia from the ammonium chloride and reusing the recovered ammonia in treating a fresh supply of methylene chloride.

4. The process of producing hexamethylenetetramme which comprises: heating a mixture comprising methylene chloride and liquid ammonia, under pressure, and separating the hexamethylenetetramine formed from the ammonium chloride formed.

5. The process of producing hexamethylenetetramme which com rises: heating a mixture of methylene c oiide and liquid a'mmona in a closed vessel, the ammonia being present at least in suicient uantit to combine with substantially all o the c lorine and the methylene groups of the methylene chloride.

6. The process of producing hexamethylenetetramine which comprises: heating a mixture of methylene chloride end liquid at least sucient uentit to combine with ammonia in a closed vessel, the ammonia. besubstantially all o the orine and meth ll0 ing present in excess of the molecular proene groups of the methylene chlori e; portions. and extracting the hexamethylenetetramine 7. The process of producing hexamethylfrom the by-produet formed. enetetremlne which comprises: heating methylene chloride and liquid ammonia, un- CARN IE B. CARTER. der pressure, the emmonin being present in ALBERT E. COXE. 

